Effect of site of placentation on pregnancy outcomes in ... - PLOS

RESEARCH ARTICLE

Effect of site of placentation on pregnancy outcomes in patients with placenta previa Lin Jing, Gu Wei*, Song Mengfan, Hou Yanyan Department of Gynecology and Obstetrics, International Peace Maternity & Child Health Hospital Affiliated to School of Medicine, Shanghai Jiao Tong University, Shanghai, China * [email protected]

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Abstract Introduction We aimed to evaluate the site of placentation on the pregnancy outcomes of patients with placenta previa.

Methods OPEN ACCESS Citation: Jing L, Wei G, Mengfan S, Yanyan H (2018) Effect of site of placentation on pregnancy outcomes in patients with placenta previa. PLoS ONE 13(7): e0200252. https://doi.org/10.1371/ journal.pone.0200252 Editor: Adi Weintraub, Soroka University Medical Center, ISRAEL Received: September 7, 2017 Accepted: June 23, 2018 Published: July 17, 2018 Copyright: © 2018 Jing et al. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. Data Availability Statement: All relevant data are within the paper and its Supporting Information file. Funding: This study was funded by the Project of Science and Technology Commission of Shanghai Municipality of China (grant number 15411964200) to GW. The URL is http://www. stcsm.gov.cn/. Competing interests: The authors have declared that no competing interests exist.

This retrospective study included 678 cases of placenta previa. Basic information and pregnancy outcome data were collected. Differences between the different placenta previa positions and pregnancy outcomes were compared using the chi-square and independent t tests. Logistic and multiple regression analyses were used to calculate the odds ratios (ORs) to determine the risk factors for PAS disorders and postpartum hemorrhage and evaluate the effect of placental attachment site on pregnancy outcomes.

Results There was no significant difference between the PAS disorders rate and the incidence of complete placenta previa depending on the type of placentation; however, placental attachment site influenced the pregnancy outcome. Placental attachment to the anterior wall was associated with shorter gestational age, low birth weight, lower Apgar score, higher prenatal bleeding rate, increased postpartum hemorrhage, longer duration of hospitalization, and higher blood transfusion and hysterectomy rates compared to cases with lateral/posterior wall placenta. Placental attachment at the incision site of a previous cesarean section significantly increased the incidence of complete placenta previa and PAS disorders compared with placental attachment at a site without incision, but did not significantly influence pregnancy outcomes. Placental attachment to the anterior wall was an independent risk factor for postpartum hemorrhage in patients with placenta previa. Placental attachment to a previous incision site was an independent risk factor for PAS disorders.

Conclusion The site of placental attachment in patients with placenta previa has an important influence on the pregnancy outcome. When the placenta is located on the anterior wall, clinicians should pay attention to the adverse pregnancy outcomes and the possibility of massive

PLOS ONE | https://doi.org/10.1371/journal.pone.0200252 July 17, 2018

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Effect of site of placentation on pregnancy outcomes in patients with placenta previa

postpartum hemorrhage. In cases of placental attachment to the uterine incision site, physicians should be highly vigilant regarding the occurrence of PAS disorders.

Introduction Placenta previa is a severe complication of pregnancy and is the most common cause of postpartum hemorrhage, which often endangers the lives of pregnant women[1]. In recent years, an increasing number of researchers believe that the placenta previa position has an important influence on the pregnancy outcome[2–3]. During the course of clinical treatment of placenta previa, obstetricians should be aware of not only the types of placenta previa (complete and partial or marginal placenta previa) but also the position of placental attachment (e.g., anterior uterine wall, posterior wall, whether the placenta overlaps a surgical scar from a previous caesarean section). Some researchers have suggested that complete placenta previa, which is characterized by placental attachment to the anterior wall covering the uterine scar, should be defined as pernicious placenta previa. Previous studies have suggested that placenta previa is often a risk factor for placenta accreta. Placenta accreta spectrum (PAS) is the latest term used to describe placenta accreta, increta, and percreta. The concept of “PAS disorders”, introduced by FIGO in 2018[4], was first defined by Luke et al.[5] which included abnormal adhesion and invasive placenta. The American College of Obstetricians and Gynecologists (ACOG)[6] and the Royal College of Obstetricians and Gynaecologists (RCOG)[7] have published guidelines to optimize the clinical management of PAS disorders based on evidence—based methods. Therefore, in order to be simple and clear, this study also used PAS disorders to describe different histopathological features of accreta placentation. However, only a few studies on placenta previa have investigated the association between the placental position and pregnancy outcome in these cases. Thus, in the present retrospective study, we aimed to examine the effects of different placental sites on pregnancy outcomes in patients with placenta previa.

Methods We have used the STROBE checklist in the design of this study.

Patient selection We retrospectively reviewed the records of 74,444 pregnant women who had been admitted to the International Peace Maternal and Child Health Hospital, Shanghai Jiao Tong University from November 2011 to October 2016. Of these, all the patients with a diagnosis of placenta previa were identified: there were 678 cases. Among the 678 cases of placenta previa, cesarean section was the mode of delivery in 676 cases and vaginal delivery was used for the remaining 2 cases (both of which had marginal placenta previa). Due to the different delivery methods (spontaneous labor and cesarean section) also have an impact on pregnancy outcome. Therefore, 2 cases of vaginal delivery were excluded and were not considered as the subject of this study. The procedures of the study received ethics approval from the relevant regional or institutional ethics committee. The name of the ethics committee is Ethics Committee of International Peace Maternal and child health hospital. Date of approval is 2/8/2016 and reference number is (GKLW)2015-61.


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The diagnosis of placenta position and PAS disorders In this study, all the subjects were recalling the final prepartum B type ultrasound images. The location of placenta was classified according to preoperative B-mode ultrasonographic findings and was finally validated in cesarean section. For all patients, placental position was detected by ultrasound in supine position within 7 days before cesarean section. The sagittal scan of the entire length of the cervix and the lower part of the uterus was first obtained in each patient. The sagittal plane of the uterus is used to determine the position of the placenta in the anterior or posterior wall. If the distance from the internal cervical ostium to the placenta edge of the anterior wall is longer than that of the posterior wall, we define it as a placenta previa on the anterior wall, or vice versa. If there is no placental tissue attached to the anterior and posterior wall on the sagittal plane, the probe should be observed at 90 degrees clockwise or counterclockwise. If the main body of the placenta is seen on the lateral wall, it is considered as the placenta previa of the lateral wall. As abnormal placentation is a spectrum disorder including both abnormal adherence (placenta accreta) and abnormal invasion (placenta increta and placenta percreta), the term PAS disorders here is used as the descriptor of the whole condition. The PAS disorders diagnosed in this study was confirmed by the intraoperative findings and postoperative pathological results.

Pregnancy outcomes Basic patient characteristics and pregnancy outcomes of all the patients were obtained. Basic information included the age, number of uterine cavity operations, placental attachment location, placenta previa type, frequency of abortion, placental attachment to the incision site, number of caesarean sections, and PAS disorders. In this study, all the patients with previous cesarean section were the transverse incision of the lower uterine segment. Uterine cavity operation refers to the operation of uterine cavity other than cesarean section and abortion, such as submucous myoma extirpation, diagnostic curettage, endometrium polyp extirpation, uterus mediastinum surgery, uterine cavity adhesion decomposition, etc. Pregnancy outcomes collected included the gestational week, postpartum hemorrhage, 1-minute Apgar score, birth weight, length of hospitalization, blood transfusion rate, PAS disorders rate, hysterectomy rate, complete placenta previa rate, and antepartum haemorrhage rate. According to the 2011 RCOG guidelines for antepartum haemorrhage (APH): APH is defined as bleeding from or in to the genital tract, occurring from 24+0 weeks of pregnancy and prior to the birth of the baby [8].

Statistical analysis Data were analyzed using Statistical Package for Social Sciences (SPSS) version 21.0 for Windows. Count data were analyzed using the chi-square test, and measured data were analyzed using a two-sample independent t test. Data analyzed using descriptive statistics were presented as the means and standard deviations (means ± SD). Significant differences were evaluated using one-way analysis of variance (ANOVA) for quantitative data and Fisher’s exact test or the chi-square test as appropriate for binomial variables. A value of P < 0.05 was considered significant. The chi-square and independent t tests were used to compare differences between the placenta previa positions and the pregnancy outcomes. Logistic and multiple regression with a stepwise entry of covariates were used to calculate odds ratios (ORs), which are presented with 95% confidence intervals (CIs), to determine the risk factors for PAS disorders and postpartum hemorrhage in patients with placenta previa and to evaluate the effect of the placental attachment position on the pregnancy outcome.


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Results General conditions of the subjects studied The incidence of placenta previa at our hospital over the past five years was approximately 0.91%. Among the 676 cases, 398 (58.9%) were central placenta previa; 46 (6.8%), partial placenta previa; and 232 (34.3%), marginal placenta previa. Furthermore, 75 of the 676 cases (11.2%) had a history of caesarean section. Among the 676 cases, there were 157 cases (23.2%) of anterior placentation, 492 cases of posterior placentation (72.8%), and 27 cases of lateral placentation (4.0%). Of the 75 patients with a history of caesarean section, the placenta was attached to the incision site in 28 cases (the main placental body was attached to the anterior wall in 27 cases and to the posterior wall in 1 case).

Factors affecting the placental attachment site in placenta previa As shown in Table 1, several factors influence the placental attachment site in placenta previa, including gravidity, parity, number of uterine cavity operations and abortions, and previous cesarean section. Age did not influence the site of placental attachment. Higher gravidity, number of uterine surgeries, or number of abortions, and the presence of previous cesarean section were all associated with a greater possibility of placental attachment to the anterior wall.

Effect of anterior placentation on pregnancy outcomes in placenta previa patients without previous caesarean section To exclude the influence of placental attachment to the site of previous incision, we compared the pregnancy outcomes in cases of placenta previa where the patient had no history of caesarean section. A total of 601 patients met the requirements, including 122 cases of placenta located in the anterior wall, 479 cases of placenta in the lateral or posterior wall. The results are shown in Table 2. There were no differences in the rate of PAS disorders or the incidence of complete placenta previa between the anterior and posterior walls. However, site of placenta previa significantly influenced the pregnancy outcome; placental attachment to the anterior wall was associated with shorter gestational age, low birth weight, lower Apgar score, higher prenatal bleeding rate, increased postpartum hemorrhage, longer duration of hospitalization, and higher blood transfusion and hysterectomy rates compared to cases with placental attachment to the posterior wall, and the differences between the two groups were significant.

Effect of placental attachment to previous cesarean section incision site on pregnancy outcomes in patients We studied the effect of placental attachment to the incision site on pregnancy outcomes. To eliminate the different effects of placental attachment to the anterior or posterior wall, here we Table 1. Factors affecting the attachment site of placenta previa. Attachment to the anterior wall (n = 157)

Attachment to the lateral or posterior wall (n = 519)

P

Age (years)

32.8±4.2

32.2±3.9

0.140

Gravidity

2.5±1.5

1.9±1.1